From 1964 to 1965, Rettig co-starred with another former child actor, Tony Dow, in the ABC television soap opera for teens Never Too Young. With the group "The TR-4", he recorded the song by that title on the Velvet Tone label. While he was the TR-4's co-manager, he did not sing with them. Rettig only co-wrote the song in hopes that the TV soap would use it as the series' theme. Producers of Never Too Young, however, chose not to use it. Rettig was subsequently cast as Frank in 1965 episode "The Firebrand" on the NBC education drama series Mr. Novak, which starred James Franciscus.